Carbon capture system recycling waste heat from condensing overhead gas of water recycle desorption column

Abstract

The application provides a carbon capture system for recycling waste heat of condensate overhead gas of a circulating water recovery desorption tower, comprising: a desorption tower with an overhead gas outlet, an absorption tower, a lean- rich liquid heat exchanger, a first flow divider, a two-stage circulating water waste heat recovery module, and a heat pump unit. The two-stage circulating water waste heat recovery module comprises a first-stage circulating water waste heat recovery unit, a second-stage circulating water waste heat recovery unit, and a fifth heat exchanger and a waste heat utilization element connected in sequence in a first water circulation loop of the first-stage circulating water waste heat recovery unit or a second water circulation loop of the second-stage circulating water waste heat recovery unit. The system recovers waste heat of the desorption tower overhead gas through the two-stage circulating water waste heat recovery unit, uses the heat pump unit to upgrade the recovered waste heat, and uses the upgraded waste heat to produce steam to supply the waste heat utilization element to heat the rich liquid and / or the lean liquid in the desorption tower. Meanwhile, the waste heat recovered by the second-stage circulating water waste heat recovery unit is also used to preheat the rich liquid.

Description

Technical Field

[0001] This invention relates to the field of carbon dioxide capture technology, and in particular to a carbon capture system for recovering waste heat from the top gas of the condenser in a circulating water desorption tower. Background Technology

[0002] Existing carbon capture processes often use absorbents such as ethanolamine (MEA) solutions to absorb CO2, and then use thermal desorption to regenerate the absorbent and generate CO2 products.

[0003] MEA (Metal-on-Anatomical Extraction) is currently the most mature and widely used post-combustion chemical absorption carbon capture technology, and its process flow has become the industry benchmark. Traditional MEA carbon capture systems include... Figure 1 As shown, the absorbent is a lean CO2 solution, which becomes a rich CO2 solution in the absorption tower. The rich solution then passes through a lean-rich solution heat exchanger and enters the desorption tower, where thermal desorption produces CO2 products, simultaneously regenerating the lean CO2 solution. The regenerated lean solution is replenished with water and absorbent before re-entering the absorption tower to complete the cycle. However, the existing carbon capture process still requires relatively high heat, cooling, and electricity consumption, and a significant amount of high-quality waste heat from the top gas of the desorption tower is wasted.

[0004] Furthermore, some carbon capture processes require creating vacuum conditions in the desorption tower. Vacuum design can be achieved through condensation and compression, but excessively high water content in the overhead gas produced by vacuum desorption leads to high compressor energy consumption and high pressure.

[0005] Therefore, for carbon capture thermal desorption processes such as MEA, effectively recovering waste heat from the overhead gas and reducing compressor energy consumption for energy-saving optimization are important requirements for carbon capture processes. Summary of the Invention

[0006] In view of the above problems, the present invention proposes a carbon capture system for recovering waste heat from the top gas of the condenser of a circulating water desorption tower to overcome or at least partially solve the above problems.

[0007] One objective of this invention is to effectively recover and utilize the waste heat from the top gas of the desorption tower, thereby reducing the cold and heat consumption during desorption.

[0008] A further objective of this invention is to reduce the energy consumption of the gas compression at the top of the tower.

[0009] Another further objective of this invention is to reduce heat loss and increase the heat exchanger temperature difference by compressing the overhead gas, thereby reducing the difficulty of waste heat recovery.

[0010] Another further objective of the present invention is to efficiently couple a heat pump with a carbon capture process, thereby recovering the heat of reaction at the absorption end while achieving thermal matching at the desorption end.

[0011] Specifically, the present invention provides a carbon capture system for recovering waste heat from the overhead gas of a circulating water recovery desorption tower condenser, comprising: Desorption tower, with a top gas outlet; The absorption tower is configured to use an absorbent liquid to absorb carbon dioxide from the gas to be treated, thereby obtaining a rich liquid. A rich-lean liquid heat exchanger is connected between an absorption tower and a desorption tower, configured to exchange heat between the rich liquid from the absorption tower and the lean liquid from the desorption tower, and to input the rich liquid after heat exchange into the desorption tower. The first distributor is located between the absorption tower and the lean-rich liquid heat exchanger. It is configured to split the rich liquid output from the absorption tower into a first rich liquid stream and a second rich liquid stream. The first rich liquid stream is input into the lean-rich liquid heat exchanger. The two-stage circulating water waste heat recovery module includes: The primary circulating water waste heat recovery unit includes a first heat exchanger and a second heat exchanger connected in the first water circulation loop; The secondary circulating water waste heat recovery unit includes a third heat exchanger and a fourth heat exchanger connected in the second water circulation loop. The fourth heat exchanger is also connected to the first distributor and the desorption tower. A fifth heat exchanger and a waste heat recovery element are sequentially connected along the water flow direction in either the first or second water circulation loop; the waste heat recovery element is also connected to a desorption tower. The heat pump unit includes a second heat exchanger, a heat exchanger for heat-upgrading the heat pump working fluid, and a fifth heat exchanger, which are sequentially connected in the working fluid loop along the flow direction of the heat pump working fluid. The first heat exchanger is also connected to the top gas outlet of the tower and is configured to allow the first circulating water flowing through it to exchange heat with the top gas output from the top gas outlet of the tower in order to recover the waste heat of the top gas. The third heat exchanger is connected to the gas path of the first heat exchanger and is configured to allow the second circulating water flowing through it to exchange heat with the overhead gas after passing through the first heat exchanger in order to further recover the waste heat of the overhead gas. With the fifth heat exchanger and the waste heat utilization element connected in the first water circulation loop, the fifth heat exchanger is located downstream of the first heat exchanger and is configured to exchange heat between the first circulating water after recovering the waste heat from the top gas of the recovery tower and the heat pump working fluid to at least partially convert it into steam; the waste heat utilization element is configured to use the first circulating water, which is at least partially converted into steam, to heat the rich liquid and / or lean liquid in the desorption tower; the second heat exchanger is located downstream of the waste heat utilization element and is configured to exchange heat between the heat pump working fluid and the first circulating water to cool the first circulating water and output the cooled first circulating water to the first heat exchanger; the fourth heat exchanger is configured to exchange heat between the second circulating water after recovering the waste heat from the top gas of the recovery tower and the second rich liquid stream from the first distributor to heat the second rich liquid stream and supply the heated second rich liquid stream to the desorption tower; With the fifth heat exchanger and the waste heat utilization element connected in the second water circulation loop, the fifth heat exchanger is located downstream of the third heat exchanger and is configured to exchange heat between the second circulating water after recovering the waste heat from the top gas of the recovery tower and the heat pump working fluid to at least partially convert it into steam; the waste heat utilization element is configured to use the second circulating water, which is at least partially converted into steam, to heat the rich liquid and / or lean liquid in the desorption tower; the fourth heat exchanger is located downstream of the waste heat utilization element and is configured to exchange heat between the second circulating water and the second rich liquid stream from the first distributor to heat the second rich liquid stream, and to supply the heated second rich liquid stream to the desorption tower; the second heat exchanger is configured to exchange heat between the heat pump working fluid and the first circulating water after recovering the waste heat from the top gas of the recovery tower to cool the first circulating water, and to output the cooled first circulating water to the first heat exchanger.

[0012] Optionally, the carbon capture system also includes: A first gas-liquid separator, connected to a first heat exchanger, is configured to perform gas-liquid separation on the overhead gas after passing through the first heat exchanger; and The first compressor is connected between the gas outlet of the first gas-liquid separator and the third heat exchanger, and is configured to compress the overhead gas after gas-liquid separation and output the compressed overhead gas to the third heat exchanger.

[0013] Optionally, the heat pump unit also includes: The sixth heat exchanger is connected in the working fluid loop and is located downstream of the fifth heat exchanger and upstream of the second heat exchanger. It is also connected to the lean and rich liquid heat exchanger and is configured to exchange heat between the heat pump working fluid and the cold lean liquid from the lean and rich liquid heat exchanger to recover the waste heat of the cold lean liquid.

[0014] Optionally, the fifth heat exchanger and the waste heat recovery element are connected in the first water circulation loop; The primary circulating water waste heat recovery unit also includes: The second distributor has an inlet connected to the first heat exchanger, a first outlet connected to the fifth heat exchanger, and a second outlet; The second gas-liquid separator has an inlet connected to the fifth heat exchanger, a gas outlet connected to the waste heat recovery element, and a liquid outlet; and The first confluencer has a first inlet connected to the second outlet of the second diverter, a second inlet connected to the waste heat recovery element, a third inlet connected to the liquid outlet of the second gas-liquid separator, and an outlet connected to the second heat exchanger. The second splitter is configured to split the first circulating water into a first water stream and a second water stream, and supply the first water stream and the second water stream to the fifth heat exchanger and the first confluencer, respectively. The second gas-liquid separator is configured to perform gas-liquid separation on the first water stream that has been at least partially converted into steam by the fifth heat exchanger, and to supply the separated steam to the waste heat utilization element. The first confluencer is configured to combine the liquid water separated by the second water stream, the liquid water separated by the second gas-liquid separator, and the condensate output by the waste heat utilization element into a first circulating water, which is then supplied to the second heat exchanger.

[0015] Optionally, the fifth heat exchanger and the waste heat recovery element are connected in the second water circulation loop; The secondary circulating water waste heat recovery unit also includes: The third gas-liquid separator has an inlet connected to the fifth heat exchanger, a gas outlet connected to the waste heat recovery element, and a liquid outlet; and The second confluencer has a first inlet connected to the liquid outlet of the third gas-liquid separator, a second inlet connected to the waste heat recovery element, and an outlet connected to the fourth heat exchanger. The third gas-liquid separator is configured to perform gas-liquid separation on the second circulating water that has been at least partially converted into steam by the fifth heat exchanger, and to supply the separated steam to the waste heat utilization element. The second confluencer is configured to combine the liquid water separated by the third gas-liquid separator and the condensate output from the waste heat recovery element into a second circulating water, which is then supplied to the fourth heat exchanger.

[0016] Optionally, the carbon capture system also includes: The third confluencer is located in the connection path between the sixth heat exchanger and the lean-rich liquid heat exchanger, and has a first inlet connected to the lean-rich liquid heat exchanger, a second inlet connected to the first gas-liquid separator, and an outlet connected to the sixth heat exchanger. The third confluencer is configured to mix the cold lean liquid from the lean-rich liquid heat exchanger with the condensate separated by the first gas-liquid separator to form a mixed lean liquid, and supply the mixed lean liquid to the sixth heat exchanger.

[0017] Optionally, the carbon capture system also includes: A fourth gas-liquid separator, connected to the third heat exchanger, is configured to perform gas-liquid separation on the overhead gas after passing through the third heat exchanger; and The second compressor is connected to the fourth gas-liquid separator and is configured to compress the gas separated by the fourth gas-liquid separator.

[0018] Optionally, the third confluencer also has a third inlet connected to the fourth gas-liquid separator. The third confluencer is configured to mix the cold lean liquid from the lean-rich liquid heat exchanger, the condensate separated by the first gas-liquid separator, and the condensate separated by the fourth gas-liquid separator into a mixed lean liquid, and supply the mixed lean liquid to the sixth heat exchanger.

[0019] Optionally, the heat pump unit is a compression heat pump unit, and the heat pump working fluid after heat exchange in the second heat exchanger evaporates into a gaseous state. The heat exchanger is a third compressor, configured to compress the gaseous heat pump working fluid; The heat pump unit also includes: A throttling valve is connected in the working fluid loop and located between the fifth and sixth heat exchangers. It is configured to reduce the pressure of the heat pump working fluid after passing through the fifth heat exchanger.

[0020] Optionally, the waste heat recovery element includes: A reboiler is connected to the bottom of the desorption tower; and / or Interstage heaters are connected to the middle section of the desorption tower.

[0021] Optionally, the absorbent is an aqueous solution of the absorbent; the absorbent is a homogeneous mixed ligand complex system, including: amine ligands, amino acid ligands, transition metal ions, and activators; The amine-containing ligand is an amino compound capable of forming monodentate, bidentate, or polydentate coordination with metal ions, including chain- or branched alkanolamines, amines, or their derivatives, wherein at least some of the amine-containing ligands have the following structural unit: HO-CR1R2-(CH2). m -CR3R4-NH2, m=1–3; Amino acid ligands include amino acids or their salts, wherein amino acids have dual coordination sites of amino and carboxyl groups; The transition metal ion contains two or more different metal centers, selected from any combination of Cr, Mn, Ni, Cu, Zn, and Co metal ions, with a total concentration of 0.001–1.0 mol / L, and forms the following reversible coordination complex system with an amine-containing ligand: Where n = 1–6, and the coordination constant is in the range of 10. 0 -10 20 They are continuously distributed within a range, thus forming a multi-level coordination energy level structure; The activator is a polyamine compound that promotes CO2 absorption kinetics, with a concentration of 0.05–3.0 mol / L.

[0022] The carbon capture system for recovering waste heat from the overhead gas of a desorption tower using circulating water provided by this invention recovers the waste heat from the overhead gas of the desorption tower in a tiered manner through two-stage circulating water waste heat recovery units. Waste heat utilization elements are connected to the water circulation loop of any one stage of the circulating water waste heat recovery unit. A heat pump unit upgrades the recovered waste heat and uses it to generate steam to supply the waste heat utilization elements, thereby heating the rich and / or lean solutions in the desorption tower. Simultaneously, the waste heat recovered by the secondary circulating water waste heat recovery unit is also supplied to preheat the diverted rich solution. Thus, the waste heat from the overhead gas of the desorption tower is effectively recovered and utilized, reducing the cooling and heating losses during desorption.

[0023] Furthermore, in the carbon capture system for the waste heat of the overhead gas of the condenser in the circulating water recovery desorption tower provided by the present invention, a first gas-liquid separator and a first compressor are set between the first heat exchanger of the first circulating water waste heat recovery unit and the third heat exchanger of the second circulating water waste heat recovery unit. The first gas-liquid separator separates the overhead gas after it has been condensed by the first circulating water through the first heat exchanger to remove the condensate, and then compresses the overhead gas. This solves the problem that the high water content of the overhead gas in the vacuum desorption tower leads to high compressor energy consumption and high pressure, effectively reducing the energy consumption of overhead gas compression, thereby reducing the overall energy consumption of the system.

[0024] Furthermore, in the carbon capture system for recovering waste heat from the overhead gas of the condenser in the circulating water recovery desorption tower provided by this invention, the overhead gas is compressed and upgraded by a first compressor before the waste heat of the compressed overhead gas is recovered. Compressing the overhead gas reduces heat loss and increases the heat exchange differential, thereby reducing the difficulty of waste heat recovery.

[0025] Furthermore, in the carbon capture system for recovering waste heat from the overhead gas of the condenser in the desorption tower provided by this invention, a heat pump recovers the low-grade waste heat of the low-temperature lean liquor. Combined with the waste heat recovery unit of the circulating water system, the waste heat recovered by the heat pump is used to generate steam to heat the rich liquor and / or medium-lean liquor in the desorption tower. This efficiently couples the heat pump with the carbon capture process, achieving not only a matching of heat and cold at the desorption end but also recovering the reaction heat at the absorption end, thereby further improving the waste heat recovery efficiency.

[0026] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below.

[0027] The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0028] To more clearly illustrate the technical solution of the present invention, some embodiments of the present invention will be described below with reference to the accompanying drawings. Those skilled in the art should understand that the same reference numerals may indicate the same or similar parts or components in different drawings; the drawings of the present invention are not necessarily drawn to scale. In the drawings: Figure 1 A schematic diagram of a conventional MEA carbon capture process system in the prior art; Figure 2 A schematic structural block diagram of a carbon capture system for the waste heat of the overhead gas of the condenser in a circulating water recovery desorption tower according to an embodiment of the present invention. Figure 3A schematic structural block diagram of a carbon capture system for the waste heat of the overhead gas of the condenser in a circulating water recovery desorption tower, according to another embodiment of the present invention. Figure 4 A schematic diagram of the structure of a carbon capture system for the waste heat of the overhead gas of the condenser in a circulating water recovery desorption tower according to another embodiment of the present invention. Figure 5 This is a schematic diagram of a carbon capture system for recovering waste heat from the overhead gas of a circulating water desorption tower according to another embodiment of the present invention. Detailed Implementation

[0029] Those skilled in the art should understand that the embodiments described below are merely a part of the embodiments of the present invention, and not all of the embodiments of the present invention. These partial embodiments are intended to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention. Based on the embodiments provided by the present invention, all other embodiments obtained by those skilled in the art without creative effort should still fall within the scope of protection of the present invention.

[0030] Furthermore, one or more examples of embodiments of the invention are illustrated in the accompanying drawings. Each example is provided by way of explanation and is not intended to limit the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to the invention without departing from the scope or spirit of the invention. For example, features shown or described as part of one embodiment may be used with another embodiment to produce yet another embodiment.

[0031] It should be noted that in the description of this invention, terms such as "center," "upper," "lower," "top," "bottom," "left," "right," "vertical," "horizontal," "inner," and "outer," which indicate direction or positional relationships, are based on the direction or positional relationships shown in the accompanying drawings. These are used merely for ease of description and do not indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on this invention. Furthermore, terms such as "first," "second," and "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0032] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection, an indirect connection through intermediate components, or a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0033] MEA (Metal-on-Anatomical Extraction) is currently the most mature and widely used post-combustion chemical absorption carbon capture technology. Traditional MEA carbon capture systems include, for example... Figure 1 As shown, the CO2-rich solution obtained in the absorber flows out from the bottom outlet of the absorber and enters the lean-rich solution heat exchanger as the RICHOUT stream. It exchanges heat with the CO2-lean solution (LEANOUT) flowing from the bottom of the stripper. After being cooled by the heat exchange, the CO2-lean solution stream S2 mixes with the supplemental absorbent MEAMU to form a mixed stream S5. S5 is then cooled and enters the absorber as the absorbent LEANIN. Simultaneously, the flue gas to be treated enters the absorber from the bottom, is treated by countercurrent contact with the absorbent, and then exits the absorber from the top as the GASOUT stream. The water stream WATEROUT drawn from the middle of the absorber mixes with the supplemental water WATERMU to form stream S1. S1 is cooled, and the resulting water stream WATERIN enters the absorber. The CO2-rich liquid, heated by the lean-rich liquid heat exchanger, is reheated to form a stream called RICHIN, which enters the desorption tower. Thermal desorption occurs within the desorption tower, and the resulting overhead gas is output from the top of the tower. After flash evaporation, CO2 product CO2OUT and condensate COND are obtained. The condensate COND is further separated to obtain streams S7 and S8.

[0034] Figure 1 The paper also presents simulation results for the conventional MEA carbon capture process. The simulation results show that the conventional flue gas carbon capture process requires a total heat consumption of approximately 5.5 GJ / ton of CO2 to the reboiler of the desorber and a cooling capacity of 5-6 GJ / ton of CO2. These cooling capacities are used for the condensation of the overhead gas in the desorber (approximately 110°C → approximately 40°C, accounting for approximately 50% of the total cooling consumption) and the cooling of the lean liquid (from 60°C → 30°C, accounting for approximately 50% of the total cooling consumption), respectively.

[0035] Further simulation using the Aspen Plus process allows for parameter optimization of traditional carbon capture processes through techniques such as rich-liquid diversion and flash regeneration, significantly reducing the required heat and cooling consumption. However, existing carbon capture engineering demonstrations require approximately 3.6–4.0 GJ / ton CO2 for heat, 2.4–4.0 GJ / ton CO2 for cooling, and 70–150 kWh / ton CO2 for electricity.

[0036] Through extensive research, the inventors of this application have innovatively recognized that in traditional carbon capture processes, directly cooling the medium-temperature lean liquid (30-50°C) after passing through a lean-rich liquid heat exchanger at the absorption end into the absorption tower would waste 0.5-2.5 GJ / ton of CO2 in heat and generate corresponding cooling losses. Simultaneously, due to differences in desorption temperature and pressure across different processes, the overhead gas in the desorption tower contains approximately 45%-90% water vapor and 25%-10% non-condensable vapor, of which the high-quality sensible heat and latent heat of phase change from recoverable gaseous water is approximately 1.5-3.5 GJ / ton of CO2. Clearly, the heat and cold in the carbon capture process are mismatched because the heat of reaction from the chemical reaction at the absorption end is difficult to recover from entering the decarbonized flue gas (or air). Furthermore, when the pressure in the desorption tower is between 0.5 bar and 1 bar, the temperature of the overhead gas is between 85°C and 120°C, which has high heat quality and can be effectively utilized. In some carbon capture processes, it is necessary to create vacuum conditions in the desorption tower. Vacuum design can be achieved through condensation and compression, but excessive water content in the overhead gas of a vacuum desorption tower can lead to high compressor energy consumption and high pressure.

[0037] Compression-type electric heat pumps based on classic working fluids such as R245fa not only have relatively mature technology and are purely electrically driven, but also can provide a large amount of high-grade heat and cooling capacity with a high energy efficiency ratio. In addition, in practical engineering applications, heat exchanger design technology using water as the working fluid is the most mature. Therefore, adding a circulating water system to the waste heat recovery of the tower top gas will reduce the engineering difficulty.

[0038] In view of this, the inventors of this application have proposed a technical solution for recovering the waste heat of the overhead gas from the desorption tower by first condensing the overhead gas and then compressing and upgrading it using circulating water. The core idea is to reduce the consumption of high-grade heat energy (especially the reboiler load) and reduce the use of cooling capacity. Specifically, an embodiment of the present invention provides a carbon capture system 100 for recovering the waste heat of the overhead gas from the desorption tower 110 using circulating water.

[0039] Figure 2 This is a schematic structural block diagram of a carbon capture system 100 for the waste heat of the overhead gas of the condenser in a circulating water recovery desorption tower 110 according to an embodiment of the present invention. Figure 3 This is a schematic structural block diagram of a carbon capture system 100 for recovering waste heat from the overhead gas of the condenser of a circulating water recovery desorption tower 110, according to another embodiment of the present invention. The heat transfer between the two is indicated by a dashed arrow from the waste heat recovery element 240 to the desorption tower 110.

[0040] See Figure 2 and Figure 3As shown, the carbon capture system 100 for recovering waste heat from the overhead gas of the desorption tower 110 generally includes a desorption tower 110 having an overhead gas outlet 111, an absorption tower 120, a lean and rich liquid heat exchanger 130, a first distributor 140, a two-stage circulating water waste heat recovery module 200, and a heat pump unit 150.

[0041] Absorption tower 120 is configured to absorb carbon dioxide from the gas to be treated using an absorbent to obtain a rich liquid. A lean-rich liquid heat exchanger 130 is connected between absorption tower 120 and desorption tower 110, and is configured to exchange heat between the rich liquid from absorption tower 120 and the lean liquid from desorption tower 110, and to input the heat-exchanged rich liquid into desorption tower 110.

[0042] The working principles of the absorption tower 120, the desorption tower 110, and the lean and rich liquid heat exchanger 130 should be known to those skilled in the art. In order not to obscure the focus of the present invention, they will not be specifically described in this application.

[0043] A first diverter 140 is disposed between the absorption tower 120 and the lean-rich liquid heat exchanger 130, configured to divert the rich liquid output from the absorption tower 120 into a first rich liquid stream and a second rich liquid stream. The first rich liquid stream is input into the lean-rich liquid heat exchanger 130. Those skilled in the art will understand that after the rich liquid is diverted, the first rich liquid stream enters the lean-rich liquid heat exchanger 130 to exchange heat with the lean liquid from the desorption tower 110.

[0044] The two-stage circulating water waste heat recovery module 200 includes a primary circulating water waste heat recovery unit 210, a secondary circulating water waste heat recovery unit 220, a fifth heat exchanger 230, and a waste heat utilization element 240. The primary circulating water waste heat recovery unit 210 includes a first heat exchanger 212 and a second heat exchanger 213 connected in the first water circulation loop 211. The secondary circulating water waste heat recovery unit 220 includes a third heat exchanger 222 and a fourth heat exchanger 223 connected in the second water circulation loop 221. The fourth heat exchanger 223 is also connected to the first distributor 140 and the desorption tower 110. The fifth heat exchanger 230 and the waste heat utilization element 240 are sequentially connected in the first water circulation loop 211 or the second water circulation loop 221 along the water flow direction. The waste heat utilization element 240 is also connected to the desorption tower 110 (specifically, it can be thermally connected).

[0045] The heat pump unit 150 includes a second heat exchanger 213, a heat exchanger 152 for heat-upgrading the heat pump working fluid, and a fifth heat exchanger 230, which are sequentially connected in the working fluid loop 151 along the flow direction of the heat pump working fluid.

[0046] The first heat exchanger 212 is also connected to the top gas outlet 111 and is configured to exchange heat between the first circulating water flowing through it and the top gas output from the top gas outlet 111 in order to recover the waste heat of the top gas.

[0047] The third heat exchanger 222 is connected to the first heat exchanger 212 via a gas path and is configured to allow the second circulating water flowing through it to exchange heat with the overhead gas after passing through the first heat exchanger 212 in order to further recover the waste heat of the overhead gas.

[0048] like Figure 2 As shown, with the fifth heat exchanger 230 and the waste heat recovery element 240 connected in the first water circulation loop 211, the fifth heat exchanger 230 is located downstream of the first heat exchanger 212 and is configured to exchange heat between the first circulating water after recovering the waste heat from the overhead gas of the recovery tower and the heat pump working fluid to at least partially convert it into steam. The waste heat recovery element 240 is configured to use the first circulating water, which is at least partially converted into steam, to heat the rich liquid and / or lean liquid in the desorption tower 110. The second heat exchanger 213 is located downstream of the waste heat recovery element 240 and is configured to exchange heat between the heat pump working fluid and the first circulating water to cool the first circulating water, and to output the cooled first circulating water to the first heat exchanger 212. The fourth heat exchanger 223 is configured to exchange heat between the second circulating water after recovering the waste heat from the overhead gas of the recovery tower and the second rich liquid stream from the first distributor 140 to heat the second rich liquid stream, and to supply the heated second rich liquid stream to the desorption tower 110.

[0049] like Figure 3 As shown, with the fifth heat exchanger 230 and the waste heat recovery element 240 connected in the second water circulation loop 221, the fifth heat exchanger 230 is located downstream of the third heat exchanger 222 and is configured to exchange heat between the second circulating water (after recovering the waste heat from the overhead gas of the recovery tower) and the heat pump working fluid to at least partially convert it into steam. The waste heat recovery element 240 is configured to use the second circulating water (at least partially converted into steam) to heat the rich and / or lean liquid in the desorption tower 110. The fourth heat exchanger 223 is located downstream of the waste heat recovery element 240 and is configured to exchange heat between the second circulating water and the second rich liquid stream from the first distributor 140 to heat the second rich liquid stream, and supply the heated second rich liquid stream to the desorption tower 110. The second heat exchanger 213 is configured to exchange heat between the heat pump working fluid and the first circulating water (after recovering the waste heat from the overhead gas of the recovery tower) to cool the first circulating water, and output the cooled first circulating water to the first heat exchanger 212.

[0050] In the carbon capture system 100 for recovering waste heat from the overhead gas of the desorption tower 110 via circulating water, as provided in this embodiment of the invention, the waste heat from the overhead gas of the desorption tower 110 is recovered in stages through two-stage circulating water waste heat recovery units. A waste heat utilization element 240 is connected to the water circulation loop of any one stage of the circulating water waste heat recovery unit 210. A heat pump unit 150 is used to upgrade the recovered waste heat and then generate steam to supply the waste heat utilization element 240, thereby heating the rich and / or lean liquids within the desorption tower 110. Simultaneously, the waste heat recovered by the secondary circulating water waste heat recovery unit 220 is also supplied to preheat the diverted rich liquid. Thus, the waste heat from the overhead gas of the desorption tower 110 is effectively recovered and utilized, reducing the cooling and heating losses during desorption.

[0051] In some embodiments, the first rich liquid stream and the second rich liquid stream may enter the desorption tower 110 through different inlets. Alternatively, the first rich liquid stream and the second rich liquid stream may also enter the desorption tower 110 through the same inlet.

[0052] Figure 4 This is a schematic diagram of a carbon capture system 100 for the waste heat of the overhead gas of the condenser in a circulating water recovery desorption tower 110 according to another embodiment of the present invention. Figure 5 This is a schematic diagram of a carbon capture system 100 for recovering waste heat from the overhead gas of the desorption tower 110 of the circulating water desorption tower according to another embodiment of the present invention. The dashed arrows from the waste heat recovery element 240 to the desorption tower 110 indicate heat transfer between the two. It should be noted that... Figure 4 and Figure 5 The separate label for absorption tower 120 refers to the same absorption tower 120. This is only for the convenience of arranging the components to more clearly show the connection relationship between the components of the carbon capture system 100.

[0053] See Figure 4 and Figure 5 As shown, in some embodiments, the carbon capture system 100 may further include a first gas-liquid separator 160. The first gas-liquid separator 160 is connected to a first heat exchanger 212 and is configured to perform gas-liquid separation on the overhead gas after passing through the first heat exchanger 212.

[0054] Furthermore, the carbon capture system 100 may also include a first compressor 170. The first compressor 170 is connected between the gas outlet of the first gas-liquid separator 160 and the third heat exchanger 222, and is configured to compress the overhead gas after gas-liquid separation and output the compressed overhead gas to the third heat exchanger 222.

[0055] In this embodiment, a first gas-liquid separator 160 and a first compressor 170 are provided between the first heat exchanger 212 of the primary circulating water waste heat recovery unit 210 and the third heat exchanger 222 of the secondary circulating water waste heat recovery unit 220. The first gas-liquid separator 160 separates the condensate from the overhead gas after it has been condensed by the first circulating water through the first heat exchanger 212 to remove the condensate. Then the overhead gas is compressed, which solves the problem that the high water content of the overhead gas caused by vacuum desorption leads to high compressor energy consumption and high pressure. This effectively reduces the energy consumption of overhead gas compression, thereby reducing the overall energy consumption of the system.

[0056] Furthermore, the overhead gas is compressed and upgraded by the first compressor 170, and then the waste heat of the compressed overhead gas is recovered. By compressing the overhead gas, heat loss is reduced and the heat exchange difference is increased, thereby reducing the difficulty of waste heat recovery.

[0057] See also Figure 4 and Figure 5 In some embodiments, the heat pump unit 150 may further include a sixth heat exchanger 153. The sixth heat exchanger 153 is connected to the working fluid loop 151 and is located downstream of the fifth heat exchanger 230 and upstream of the second heat exchanger 213, and is connected to the lean-rich liquid heat exchanger 130, configured to exchange heat between the heat pump working fluid and the cold lean liquid from the lean-rich liquid heat exchanger 130 to recover the waste heat of the cold lean liquid.

[0058] In this embodiment, a heat pump is used to recover the low-grade waste heat of the low-temperature lean liquor. Combined with a circulating water waste heat recovery unit, the waste heat recovered by the heat pump is used to generate steam to heat the rich liquor and / or medium-lean liquor in the desorption tower 110. This efficiently couples the heat pump with the carbon capture process, not only achieving heat matching at the desorption end but also recovering the reaction heat at the absorption end, thereby further improving the waste heat recovery efficiency.

[0059] See Figure 4 As shown, in some embodiments, the fifth heat exchanger 230 and the waste heat recovery element 240 are connected in the first water circulation loop 211. The primary circulating water waste heat recovery unit 210 may further include a second distributor 214, a second gas-liquid separator 215, and a first confluencer 216. The second distributor 214 has an inlet 214a connected to the first heat exchanger 212, a first outlet 214b connected to the fifth heat exchanger 230, and a second outlet 214c. The second gas-liquid separator 215 has an inlet 215a connected to the fifth heat exchanger 230, a gas outlet 215b connected to the waste heat recovery element 240, and a liquid outlet 215c. The first confluencer 216 has a first inlet 216a connected to the second outlet 214c of the second diverter 214, a second inlet 216b connected to the waste heat utilization element 240, a third inlet 216c connected to the liquid outlet 215c of the second gas-liquid separator 215, and an outlet 216d connected to the second heat exchanger 213.

[0060] The second distributor 214 is configured to split the first circulating water into a first water stream and a second water stream, and supply the first water stream and the second water stream to the fifth heat exchanger 230 and the first confluencer 216, respectively. The second gas-liquid separator 215 is configured to perform gas-liquid separation on the first water stream, which is at least partially converted into steam by the fifth heat exchanger 230, and supply the separated steam to the waste heat utilization element 240. The first confluencer 216 is configured to combine the second water stream, the liquid water separated by the second gas-liquid separator 215, and the condensate output from the waste heat utilization element 240 into the first circulating water, and then supply it to the second heat exchanger 213.

[0061] In actual operation, the first circulating water exchanges heat with the overhead gas in the first heat exchanger 212, and then is divided into a first water stream and a second water stream by the second splitter 214. The first water stream exchanges heat with the heat pump working fluid in the fifth heat exchanger 230, thus converting at least part of it into steam. It then enters the second gas-liquid separator 215 for gas-liquid separation. The separated steam enters the waste heat utilization element 240 to heat the rich liquid and / or lean liquid in the desorption tower 110, and then condenses itself into water. The condensate output from the waste heat utilization element 240, the liquid water separated by the second gas-liquid separator 215, and the second water stream are combined by the first merger 216 to form the first circulating water, which then enters the second heat exchanger 213 to exchange heat with the heat pump working fluid and is thus cooled. The cooled first circulating water then enters the first heat exchanger 212 to exchange heat with the overhead gas, thereby achieving the purpose of condensing the overhead gas and completing the circulation of the first circulating water.

[0062] After the second circulating water exchanges heat with the overhead gas in the third heat exchanger 222, it enters the fourth heat exchanger 223 to exchange heat with the second rich liquid stream from the first distributor 140 to preheat the second rich liquid stream, and then enters the third heat exchanger 222 to complete the circulation of the second circulating water.

[0063] See Figure 5As shown, in some embodiments, the fifth heat exchanger 230 and the waste heat recovery element 240 are connected in the second water circulation loop 221. The secondary circulating water waste heat recovery unit 220 may further include a third gas-liquid separator 224 and a second confluencer 225. The third gas-liquid separator 224 has an inlet 224a connected to the fifth heat exchanger 230, a gas outlet 224b connected to the waste heat recovery element 240, and a liquid outlet 224c. The second confluencer 225 has a first inlet 225a connected to the liquid outlet 224c of the third gas-liquid separator 224, a second inlet 225b connected to the waste heat recovery element 240, and an outlet 225c connected to the fourth heat exchanger 223. The third gas-liquid separator 224 is configured to perform gas-liquid separation on the second circulating water that has been at least partially converted into steam by the fifth heat exchanger 230, and to supply the separated steam to the waste heat recovery element 240. The second confluencer 225 is configured to combine the liquid water separated by the third gas-liquid separator 224 and the condensate output by the waste heat utilization element 240 into a second circulating water, which is then supplied to the fourth heat exchanger 223.

[0064] In actual operation, the first circulating water exchanges heat with the overhead gas in the first heat exchanger 212, and then enters the second heat exchanger 213 to exchange heat with the heat pump working fluid, thereby being cooled. The cooled first circulating water then enters the first heat exchanger 212 again to exchange heat with the overhead gas, so as to achieve the purpose of condensing the overhead gas, thus completing the circulation of the first circulating water.

[0065] The second circulating water, after exchanging heat with the overhead gas in the third heat exchanger 222, enters the fifth heat exchanger 230 to exchange heat with the heat pump working fluid, thus converting at least partially into steam. It then enters the third gas-liquid separator 224 for gas-liquid separation. The separated steam enters the waste heat utilization element 240 to heat the rich and / or lean liquid in the desorption tower 110, and condenses itself into water. The condensate output from the waste heat utilization element 240 and the liquid water separated by the third gas-liquid separator 224 are combined by the second confluencer 225 to form the second circulating water. This water then enters the fourth heat exchanger 223 to exchange heat with the second rich liquid stream from the first distributor 140 to preheat the second rich liquid stream, and then enters the third heat exchanger 222, thus completing the second circulating water cycle.

[0066] See also Figure 4 and Figure 5In some embodiments, the carbon capture system 100 may further include a third confluencer 180. The third confluencer 180 is disposed in the connection path between the sixth heat exchanger 153 and the lean-rich liquid heat exchanger 130, and has a first inlet 180a connected to the lean-rich liquid heat exchanger 130, a second inlet 180b connected to the first gas-liquid separator 160, and an outlet 180d connected to the sixth heat exchanger 153. The third confluencer 180 is configured to mix the cold lean liquid from the lean-rich liquid heat exchanger 130 with the condensate separated by the first gas-liquid separator 160 to form a mixed lean liquid, and supply the mixed lean liquid to the sixth heat exchanger 153. Thus, the heat pump working fluid can simultaneously recover the waste heat from the cold lean liquid and the condensate separated from the overhead gas, thereby further improving waste heat utilization efficiency.

[0067] In some embodiments, the carbon capture system 100 may further include a fourth gas-liquid separator 190. The fourth gas-liquid separator 190 is connected to the third heat exchanger 222 and configured to perform gas-liquid separation on the overhead gas after passing through the third heat exchanger 222.

[0068] In some embodiments, the third confluencer 180 may also have a third inlet 180c connected to the fourth gas-liquid separator 190. The third confluencer 180 is configured to mix the cold lean liquid from the lean-rich liquid heat exchanger 130, the condensate separated by the first gas-liquid separator 160, and the condensate separated by the fourth gas-liquid separator 190 into a mixed lean liquid, and supply the mixed lean liquid to the sixth heat exchanger 153. This embodiment can further recover the waste heat of the overhead gas condensate.

[0069] In some embodiments, the sixth heat exchanger 153 may also be connected to the absorption tower 120 to supply the cooled lean liquid or mixed lean liquid to the absorption tower 120.

[0070] In some embodiments, the carbon capture system 100 may further include a second compressor 191. The second compressor 191 is connected to a fourth gas-liquid separator 190 and configured to compress the gas separated by the fourth gas-liquid separator 190 to obtain compressed CO2 product gas.

[0071] In some embodiments, the heat pump unit 150 may be a compression heat pump unit 150. The heat pump working fluid, after heat exchange in the second heat exchanger 213, evaporates into a gaseous state. The heat exchanger 152 is a third compressor 154, configured to compress the gaseous heat pump working fluid. The heat pump unit 150 also includes a throttling valve 155 connected in the working fluid loop 151 and located downstream of the fifth heat exchanger 230 and upstream of the second heat exchanger 213, configured to depressurize the heat pump working fluid after passing through the fifth heat exchanger 230.

[0072] In some embodiments, where the heat pump unit 150 includes a sixth heat exchanger 153, a throttle valve 155 is located between the fifth heat exchanger 230 and the sixth heat exchanger 153 and is configured to depressurize the heat pump working fluid after passing through the fifth heat exchanger 230.

[0073] By using a compression heat pump, the recovered waste heat is efficiently upgraded, thereby improving the efficiency of waste heat utilization.

[0074] The heat pump working fluid can be a commonly used heat pump working fluid, such as R245fa, as needed.

[0075] In some embodiments, the waste heat utilization element 240 may be a reboiler connected to the bottom of the desorption tower 110 for heating the lean liquor in the desorption tower 110.

[0076] In other embodiments, the waste heat utilization element 240 may be an interstage heater connected to the middle section of the desorption tower 110 for heating the rich liquid in the desorption tower 110.

[0077] In some other embodiments, the waste heat utilization element 240 may include a reboiler and an interstage heater.

[0078] By utilizing the recovered waste heat for interstage heating, heat exchange in the rich liquid can be promoted, thereby improving desorption efficiency and increasing CO2 production.

[0079] Specific examples of gas-liquid separators include flash tanks, etc.

[0080] Those skilled in the art will understand that in order to facilitate the flow of fluids (such as lean liquid, rich liquid, overhead gas, heat pump working fluid, circulating water), devices that provide circulation driving force, such as pumps, can be provided in each loop, circuit, or flow path.

[0081] The absorbent solution is an aqueous solution of the absorbent. In some embodiments, the absorbent is a homogeneous mixed ligand complex system, comprising: an amine-containing ligand, an amino acid ligand, a transition metal ion, and an activator. The amine-containing ligand serves as the first ligand, and the amino acid ligand serves as the second ligand.

[0082] In some optional embodiments, the amine-containing ligand is an amino compound capable of forming monodentate, bidentate, or polydentate coordination with metal ions, including chain or branched alkanolamines, amines, or derivatives thereof, wherein at least a portion of the amine-containing ligand has the structural unit HO-CR1R2-(CH2). m -CR3R4-NH2, m=1–3.

[0083] In some alternative embodiments, the amino acid ligand comprises an amino acid or a salt thereof, wherein the amino acid has a dual coordination site of an amino group and a carboxyl group.

[0084] In some optional embodiments, the transition metal ion comprises two or more different metal centers, selected from any combination of metal ions such as Cr, Mn, Ni, Cu, Zn, and Co, and its total concentration in the homogeneous mixed ligand complex system is 0.001–1.0 mol / L, and it forms the following reversible coordination complex system with the amine-containing ligand: Where n = 1–6, and the coordination constant is in the range of 10. 0 -10 20 They are continuously distributed within a range, thus forming a multi-level coordination energy level structure.

[0085] In some optional embodiments, the activator is a polyamine compound that promotes CO2 absorption kinetics, and its concentration in the homogeneous mixed ligand complex system is 0.05–3.0 mol / L.

[0086] In the absorbent system of the present invention, amine ligands and amino acid ligands form a mixed ligand complex network with dynamic exchange characteristics under the action of transition metal ions. During the CO2 absorption and desorption process, the coordination structure of this complex network undergoes reversible reconstruction, so that the heat of reaction is stored and released at least partly in the form of coordination bond energy, thereby realizing the heat buffering of heat absorption and the energy compensation of heat desorption.

[0087] This absorbent system can achieve CO2 desorption and regeneration in a temperature range of 80-120°C, and compared with the corresponding amine system without metal ions, it exhibits reduced desorption energy consumption or reboiler heat load.

[0088] Transition metal ions regulate the electronic structure and bond energy distribution of amine-containing ligands through coordination-inductive effects, thereby increasing the bond dissociation energy of the α-carbon adjacent to the amine group and inhibiting oxidative degradation through at least one of the following pathways: a) reducing the rate of free radical generation; b) catalyzing the decomposition of peroxy radicals; c) capturing reaction intermediate free radicals to form stable complexes; d) altering the reaction pathway to inhibit the propagation of chain reactions.

[0089] When the absorbent system contains two or more transition metal ions, the bimetallic or multimetallic system can form a synergistic catalytic and energy regulation effect through electronic coupling or redox cycle between different metal centers, thereby simultaneously achieving absorption heat management and anti-degradation performance improvement.

[0090] The following is based on Figure 4 and Figure 5 The carbon capture system 100 for the waste heat of the overhead gas of the condenser in the circulating water recovery desorption tower 110 shown is a specific embodiment. The technical effect of the technical solution of the present invention is verified by simulation.

[0091] Taking a carbon capture unit with a capacity of 10,000 tons of CO2 per year as an example, vacuum desorption is performed at 0.5 bar. Since the parameters of the rich liquor correspond to the scale, the simulation starts directly from the rich liquor at the bottom outlet of the 120 absorber. The parameters of the low-temperature rich liquor are shown in Table 1 below (corresponding to a carbon load of 0.45 mol / mol).

[0092] Table 1. Rich solution injection conditions for carbon capture process

[0093] Figure 4 In the carbon capture system 100 for recovering waste heat from the overhead gas of the desorption tower 110, as shown, the first-stage circulating water directly exchanges heat with the overhead gas. After heat exchange, a portion of the circulating water is diverted to a heat pump to generate steam, which is then supplied to the waste heat utilization element 240. The other portion mixes with the condensed steam stream, transferring heat to the heat pump system and cooling itself to approximately 40°C. It then returns to the first heat exchanger 212 for recycling the waste heat from the overhead gas. The second-stage circulating water is used to recover the waste heat from the compressed overhead gas and supplies the waste heat to the preheated rich liquid. Figure 5 In the carbon capture system 100 for recovering waste heat from the overhead gas of the condenser in the circulating water desorption tower 110 shown, the water used to generate steam is no longer supplied by the first-stage circulating water, but by the second-stage circulating water, which has a smaller volume and lower operating load.

[0094] Simulation results show that the technical solution of the present invention has the following beneficial effects: (1) Desorption does not require an external cold source or an external heat source, thus achieving full-process electrification.

[0095] (2) The gas loss at the top of the compression tower is reduced, and the difficulty of waste heat recovery is greatly reduced. The heat exchange end difference is large.

[0096] (3) Low vacuum pressure, low compression energy consumption, and low engineering difficulty. The energy consumption of the top gas of the compression tower can be as low as 38kW, which can reduce the energy consumption of the first stage compression by 85%.

[0097] (4) Compared with similar processes, it can efficiently recover waste heat while completing vacuum desorption. Especially for Figure 5 The system shown has lower process complexity and can reduce the number of equipment such as distributors, pumps, and storage tanks.

[0098] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0099] Therefore, those skilled in the art should recognize that although numerous exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Thus, the scope of the present invention should be understood and construed as covering all such other variations or modifications.

Claims

1. A carbon capture system for recovering waste heat from the overhead gas of a circulating water desorption tower condenser, comprising: Desorption tower, with a top gas outlet; The absorption tower is configured to use an absorbent liquid to absorb carbon dioxide from the gas to be treated, thereby obtaining a rich liquid. A rich-lean liquid heat exchanger is connected between the absorption tower and the desorption tower, configured to exchange heat between the rich liquid from the absorption tower and the lean liquid from the desorption tower, and to input the rich liquid after heat exchange into the desorption tower. A first distributor is disposed between the absorption tower and the lean-rich liquid heat exchanger, and is configured to split the rich liquid output from the absorption tower into a first rich liquid stream and a second rich liquid stream, wherein the first rich liquid stream is input into the lean-rich liquid heat exchanger. The two-stage circulating water waste heat recovery module includes: The primary circulating water waste heat recovery unit includes a first heat exchanger and a second heat exchanger connected in the first water circulation loop; The secondary circulating water waste heat recovery unit includes a third heat exchanger and a fourth heat exchanger connected in the second water circulation loop, wherein the fourth heat exchanger is also connected to the first distributor and the desorption tower; and A fifth heat exchanger and a waste heat recovery element are sequentially connected along the water flow direction in either the first or second water circulation loop; the waste heat recovery element is also connected to the desorption tower. A heat pump unit includes a second heat exchanger, a heat exchanger for heat-upgrading the heat pump working fluid, and the fifth heat exchanger, which are sequentially connected in the working fluid loop along the flow direction of the heat pump working fluid. The first heat exchanger is also connected to the top gas outlet of the tower and is configured to exchange heat between the first circulating water flowing through it and the top gas output from the top gas outlet of the tower in order to recover the waste heat of the top gas. The third heat exchanger is connected to the gas path of the first heat exchanger and is configured to allow the second circulating water flowing through it to exchange heat with the overhead gas after passing through the first heat exchanger in order to further recover the waste heat of the overhead gas. With the fifth heat exchanger and the waste heat utilization element connected in the first water circulation loop, the fifth heat exchanger is located downstream of the first heat exchanger and is configured to exchange heat between the first circulating water after recovering the waste heat from the top gas of the recovery tower and the heat pump working fluid to at least partially convert it into steam; the waste heat utilization element is configured to use the first circulating water, which is at least partially converted into steam, to heat the rich liquid and / or lean liquid in the desorption tower; the second heat exchanger is located downstream of the waste heat utilization element and is configured to exchange heat between the heat pump working fluid and the first circulating water to cool the first circulating water, and to output the cooled first circulating water to the first heat exchanger; the fourth heat exchanger is configured to exchange heat between the second circulating water after recovering the waste heat from the top gas of the recovery tower and the second rich liquid stream from the first distributor to heat the second rich liquid stream, and to supply the heated second rich liquid stream to the desorption tower. With the fifth heat exchanger and the waste heat utilization element connected in the second water circulation loop, the fifth heat exchanger is located downstream of the third heat exchanger and is configured to exchange heat between the second circulating water after recovering the waste heat from the top gas of the recovery tower and the heat pump working fluid to at least partially convert it into steam; the waste heat utilization element is configured to use the second circulating water, which is at least partially converted into steam, to heat the rich liquid and / or lean liquid in the desorption tower; the fourth heat exchanger is located downstream of the waste heat utilization element and is configured to exchange heat between the second circulating water and the second rich liquid stream from the first distributor to heat the second rich liquid stream, and supply the heated second rich liquid stream to the desorption tower; the second heat exchanger is configured to exchange heat between the heat pump working fluid and the first circulating water after recovering the waste heat from the top gas of the recovery tower to cool the first circulating water, and output the cooled first circulating water to the first heat exchanger.

2. The carbon capture system for the waste heat of the overhead gas of the condenser in the circulating water recovery desorption tower according to claim 1, characterized in that, Also includes: A first gas-liquid separator is connected to the first heat exchanger and is configured to perform gas-liquid separation on the overhead gas after passing through the first heat exchanger. as well as A first compressor is connected between the gas outlet of the first gas-liquid separator and the third heat exchanger, configured to compress the overhead gas after gas-liquid separation and output the compressed overhead gas to the third heat exchanger.

3. The carbon capture system for the waste heat of the overhead gas of the condenser in the circulating water recovery desorption tower according to claim 2, characterized in that, The heat pump unit also includes: A sixth heat exchanger is connected to the working fluid loop and located downstream of the fifth heat exchanger and upstream of the second heat exchanger, and is connected to the lean-rich liquid heat exchanger, configured to allow the heat pump working fluid to exchange heat with the cold lean liquid from the lean-rich liquid heat exchanger to recover the waste heat of the cold lean liquid.

4. The carbon capture system for the waste heat of the overhead gas of the condenser in the circulating water recovery desorption tower according to claim 3, characterized in that, The fifth heat exchanger and waste heat recovery element are connected to the first water circulation loop; The primary circulating water waste heat recovery unit also includes: The second distributor has an inlet connected to the first heat exchanger, a first outlet connected to the fifth heat exchanger, and a second outlet; The second gas-liquid separator has an inlet connected to the fifth heat exchanger, a gas outlet connected to the waste heat recovery element, and a liquid outlet; and The first confluencer has a first inlet connected to the second outlet of the second diverter, a second inlet connected to the waste heat utilization element, a third inlet connected to the liquid outlet of the second gas-liquid separator, and an outlet connected to the second heat exchanger. The second splitter is configured to split the first circulating water into a first water stream and a second water stream, and supply the first water stream and the second water stream to the fifth heat exchanger and the first confluencer, respectively. The second gas-liquid separator is configured to perform gas-liquid separation on the first water stream that has been at least partially converted into steam by the fifth heat exchanger, and to supply the separated steam to the waste heat utilization element. The first confluencer is configured to combine the second water stream, the liquid water separated by the second gas-liquid separator, and the condensate output by the waste heat utilization element into a first circulating water, which is then supplied to the second heat exchanger.

5. The carbon capture system for the waste heat of the overhead gas of the condenser in the circulating water recovery desorption tower according to claim 3, characterized in that, The fifth heat exchanger and waste heat recovery element are connected to the second water circulation loop; The secondary circulating water waste heat recovery unit also includes: The third gas-liquid separator has an inlet connected to the fifth heat exchanger, a gas outlet connected to the waste heat recovery element, and a liquid outlet; and The second confluencer has a first inlet connected to the liquid outlet of the third gas-liquid separator, a second inlet connected to the waste heat utilization element, and an outlet connected to the fourth heat exchanger. The third gas-liquid separator is configured to perform gas-liquid separation on the second circulating water that has been at least partially converted into steam by the fifth heat exchanger, and to supply the separated steam to the waste heat utilization element. The second confluencer is configured to combine the liquid water separated by the third gas-liquid separator and the condensate output by the waste heat utilization element into a second circulating water, which is then supplied to the fourth heat exchanger.

6. The carbon capture system for the waste heat of the overhead gas of the condenser in the circulating water recovery desorption tower according to any one of claims 3-5, characterized in that, Also includes: A third confluencer is disposed in the connection path between the sixth heat exchanger and the lean-rich liquid heat exchanger, and has a first inlet connected to the lean-rich liquid heat exchanger, a second inlet connected to the first gas-liquid separator, and an outlet connected to the sixth heat exchanger. The third confluencer is configured to mix the cold lean liquid from the lean-rich liquid heat exchanger with the condensate separated by the first gas-liquid separator to form a mixed lean liquid, and supply the mixed lean liquid to the sixth heat exchanger.

7. The carbon capture system for the waste heat of the overhead gas of the condenser in the circulating water recovery desorption tower according to claim 6, characterized in that, Also includes: The fourth gas-liquid separator is connected to the third heat exchanger and is configured to perform gas-liquid separation on the overhead gas after passing through the third heat exchanger. as well as The second compressor is connected to the fourth gas-liquid separator and is configured to compress the gas separated by the fourth gas-liquid separator; The third confluencer also has a third inlet connected to the fourth gas-liquid separator. The third confluencer is configured to mix the cold lean liquid from the lean-rich liquid heat exchanger, the condensate separated by the first gas-liquid separator, and the condensate separated by the fourth gas-liquid separator into a mixed lean liquid, and supply the mixed lean liquid to the sixth heat exchanger.

8. The carbon capture system for the waste heat of the overhead gas of the condenser in the circulating water recovery desorption tower according to any one of claims 3-5, characterized in that, The heat pump unit is a compression heat pump unit, and the heat pump working fluid after heat exchange in the second heat exchanger evaporates into a gaseous state. The heat exchanger is a third compressor, configured to compress the gaseous heat pump working fluid; The heat pump unit also includes: A throttling valve, connected in the working fluid loop and located between the fifth heat exchanger and the sixth heat exchanger, is configured to reduce the pressure of the heat pump working fluid after passing through the fifth heat exchanger.

9. The carbon capture system for the waste heat of the overhead gas of the condenser in the circulating water recovery desorption tower according to claim 1, characterized in that, The waste heat recovery element includes: A reboiler is connected to the bottom of the desorption tower; and / or An interstage heater is connected to the middle section of the desorption tower.

10. The carbon capture system for the waste heat of the overhead gas of the condenser in the circulating water recovery desorption tower according to claim 1, characterized in that, The absorbent solution is an aqueous solution of the absorbent; the absorbent is a homogeneous mixed ligand complex system, comprising: amine ligands, amino acid ligands, transition metal ions, and activators; The amine-containing ligand is an amino compound capable of forming monodentate, bidentate, or polydentate coordination with metal ions, including chain- or branched alkanolamines, amines, or their derivatives, wherein at least a portion of the amine-containing ligand has the following structural unit: HO-CR1R2-(CH2). m -CR3R4-NH2, m=1–3; The amino acid ligand comprises an amino acid or a salt thereof, wherein the amino acid has dual coordination sites of amino and carboxyl groups; The transition metal ion contains two or more different metal centers, selected from any combination of Cr, Mn, Ni, Cu, Zn, and Co metal ions, with a total concentration of 0.001–1.0 mol / L, and forms the following reversible coordination complex system with the amine-containing ligand: Where n = 1–6, and the coordination constant is in the range of 10. 0 -10 20 They are continuously distributed within a range, thus forming a multi-level coordination energy level structure; The activator is a polyamine compound that promotes CO2 absorption kinetics, and its concentration is 0.05–3.0 mol / L.

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